This invention relates to phased array antenna systems, and particularly to reduction of phase quantization errors in phase array systems used for direction finding applications.
In his copending application, Ser. No. 872,525 filed Jan. 26, 1978, Richard F. Frazita describes a phased array antenna having reduced phase quantization errors. Pertinent portions of that application are incorporated herein by reference. The Frazita application discloses an array antenna wherein one element in each pair of elements on an array aperture is provided with a phase adjustment in the coupling network. The phase adjustment has a phase length which is equal to one-half the smallest phase step of the digital phase shifters used in the coupling network. The phase adjustment results in an offset in the radiation angles at which symmetrically located phase shifters change state. This offset of radiation angles effectively reduces the maximum phase quantization error from an amount equal to the value of the smallest phase shifter step to an amount equal to one-half the valve of the smallest phase shifter step.
It is an object of the present invention to provide a phased array antenna wherein phase quantization errors are reduced without the use of phase adjustments in the antenna coupling network.